Cyclohexane-dicarboxylic imide type functional fluids



United States Patent ce 3317427 Patented May 2, 1967 It has now been found that the imides of the formula 3,317,427 CH 00 CYCLDHEXANE-DICARBOXYLIC IMIDE TYPE FUNCTIONAL FLUIDS (3H2 (I311 Joachim Dazzi, Riehen, Switzerland, assignor to Geigy 5 CH2 OH 1 Chemical Corporation, Greenburgh, N.Y., a corporation of Delaware H O O (I) No Drawing. Filed May 10, 1965, Ser. No. 454,678 Claims priority, application Switzerland, May 12, 1964, 6,143/ 64 8 Claims. (CL 252-49.6)

The present invention concerns the use of imides which are liquid under the conditions for use as functional fluids, as well as compositions of matter which contain the imides usable according to the invention and other usual functional fluids and, optionally, additives which improve or modify their properties.

By the term functional fluid (lubricant fluid for machines) is meant a fluid without the presence of which a machine cannot perform its function. Lubricants, hydraulic fluids, damping and brake fluids, dielectric fluids, heat-transferring agents, for example, are included in this term (cf. Roger E. Hatton, Introduction to Hydraulic Fluids, Reinhold Publishing Corporation, New York, 1962, -p. 5

Very high demands are made of functional fluids such as are used in modern machines and systems which function at very high temperatures, e.g. gas turbine aircraft engines; for example:

(1) They must be liquid under the conditions for use and must be capable of forming a lubricant film on the most varied materials, in particular on metals;

(2) They must not be very volatile and must be substantially stable to heat;

(3) They should not be corrosive and, above all, should not form any acid decomposition products;

(4) They should retain their lubricant properties over as large a temperature range as possible, i.e. their viscosity should be as independent as possible from the temperature;

(5) Their solidification point should be as low as possible and, on the other hand, the boiling point should be as high as possible.

With many of these necessary properties, one excludes the other and it is thus difficult to find substances which meet these requirements to such an extent that, for ex ample, they can be used as lubricants for gas turbines.

Up to now, the following types of compounds, for example, have been used as high boiling functional fluids:

(a) High boiling organic esters such as diesters of dicarboxylic acids, e.g. adipic or sebacic acid, with alcohols having medium to long carbon chains, also triesters of trimethylol propane and higher fatty acids or esters of wherein each of R and R" represents hydrogen or, together they represent a lower alkylene group having 1 or 2 carbon atoms, a preferred subclass of compounds being that in which R and R" together represent the methylene group, and R represents an alkyl group having 6 to 18, and still more preferably 8 to 12 carbon atoms in a straight chain, have particularly advantageous properties as functional fluids, i.e. their properties represent a highly suitable compromise of the required properties mentioned hereinbefore.

Some of the imides according to the invention are known or they can be produced by processes known per se.

The use of cyclic N-alkyl imides as lubricants is known from the literature; thus, in Belgian Patent'No. 623,333, in particular N-alkyl succinimides having long chained substituents are suggested as lubricants. However, such N-alkyl succinimides, the alkyl radical of which has 8 to 12 carbon atoms, are solid at room temperature. In contrast thereto, N-alkyl imides used according to the invention, particularly those the alkyl radical R of which has 8 to 12 carbon atoms, are fluids which, in the pure state, melt by at least 40 C. lower than the N-alkyl succinimides having identical nitrogen substituents. Mixtures of N- alkyl imides usable according to the invention such as are formed when produced from technically obtainable primary amines, often solidify only at 60 C. Thus, in contrast to the previously known N-alkyl succinimides, N-alkyl imides according to the invention can also be used under arctic or stratospheric conditions. In addition, the N-alkyl imides according to the invention have considerably better stability to oxidation than the previously known N-alkyl succinimides. Thanks to this property, they can also be used at higher temperatures as lubricants, at which temperatures the previously known succinimides are insuflicient. Another advantage of the N-alkyl imides used according to the invention over the previously known N-alkyl succinimides is that, with identical N-substitution, they are considerably less volatile.

The imides used according to the invention are colorless to pale yellowish fluid oils of decreasing consistency at room temperature.

Compared with previously known products used as gas turbine lubricant oils, the N-alkyl imides used according to the invention are distinguished by particularly good stability to heat with, at the same time, good lower temperature properties. For instance, they decompose only at over 3 C. whilst the organic esters which up to now have been the most stable to heat, e.g. the triesters of fatty acids with trimethylol propane, are unusable even above 360 C. Another advantage of the N-alkyl imides over lubricants based on organic and also inorganic esters is that, in contrast to the esters, they form almost no acid decomposition products on thermal decomposition. This limited tendency of the imides of Formula I to form acid decomposition products which are responsible for the corrosive action, is shown, for example, by the fact that on keeping N-decylor N-dodecylcyclohexane-1,2-dicarboxylic acid imide (see further below) at 400 C. for 6 hours under an at mosphere of nitrogen, the volatile compounds formed and also the residue are neutral Whilst the substances formed from the triester of trimethylol propane and pelargonic acid at 360 C. under an atmosphere of nitrogen have an acid number for volatile parts and residue combined of about 78 mg. KOH/g. Another advantage of the imides according to the invention compared with lubricants based on alkyl esters of organic acids, on phosphoric acid esters, alkyl silicons and silicates, consists in that they are more stable to the influence of 'y-rays. In addition, the alkyl imides of Formula I used according to the invention surpass the lubricants based on organic esters in that they do not swell certain plastics used for the production of gasket materials unduly.

Compared with the silicone oils and polyphenyl ethers, the imides according to the invention are distinguished by a better lubricating effect and also, moreover, compared with the polyphenyl ethers, also by a lower solidifying point, a viscosity which is less dependent on temperature and a lower density.

The imides of Formula I used according to the invention are suitable for the lubrication of the most various surfaces; for instance, they considerably reduce the friction of metal on metal and also, that of metal on silicates such as glass.

An advantage of the imides used according to the invention is their surprisingly good miscibility with other usual functional fluids, for example with those based on organic esters, polyaryl ethers, polyalkyl melamines, high boiling phosphoric acid esters, high boiling mineral oils, certain silicone oils or orthosilicates. This favorable miscibility makes the production of special lubricants possible in that the properties required for a certain use but which cannot be attained by the individual components, can be obtained by the production of suitable mixtures.

A further advantage of the imides usable according to the invention consists in their relatively high dielectric constant so that they can be used as dielectrics. In addition, they are non-toxic under practical conditions (oral DL in the mouse: 5000' mg./kg.).

The smaller the number of carbon atoms in R in the imides of Formula I, the lower is their melting point. Thus, imides having a short -N-alkyl chain are preferred with regard to low temperature properties. On the other hand, volatility decreases with the increasing number of carbon atoms so that, in this connection, imides having a long N-alkyl chain are preferred.

Mixtures as defined of imides of Formula I are particularly suitable as functional fluids, preferably those mixtures in which the number of compounds in which R is a hexyl group is less than the sum of the number of compounds in which R is an octyl, decyl or dodecyl radical, is at least 95% and the number of compounds in which R is an alkyl radical higher than the dodecyl radical, is less than 5%; these proportions are percentages by weight calculated on the total weight of the mixture. Such mixtures are the most advantageous compromise between low solidification point and slight volatility. Also, imides of Formula I wherein R and R" are hydrogen are preferred for reasons of economy.

Especially, when they are to be used at temperatures of over 150 C. to make use of their favorable stability to heat, they are mixed advantageously with antioxidants in order to hinder the auto-oxidation which sets in above this temperature. The amount of antioxidant is about 0.01 to 5% by weight of the total weight of the lubricant or functional fluid.

As antioxidants there are usable secondary monoamines, particularly diarylamines having carbocyclic or heterocyclic radicals as well as aromatic diamines the amine substituents, preferably secondary, of which are in the ortho or, advantageously, the para-positions.

Examples of carbocyclic and heterocyclic aromatic diaryl amines which can be used as antioxidants are diphenylamines, phenylnaphthylamines, phenylacenaphthenylamines; .4,4-dinaphthylaminodiphenyl; thiazolyl- (2)-naphthylamines; examples of aromatic diamines are N,N-diphenyl-p-phenylenediamine, N,N-dioctyl-p-phenylenediamine, N,N-dicyclohexyl-p-phenylenediamine, N- sec. butyl-N'-phenyl-p-phenylenediamine, N,N'-bis-('yaminopropyl -p-phenylenediamine.

Hydroxyl-substituted aromates can be employed as antioxidants particularly at not too high temperatures (i.e under ZOO-300 C. depending on type of the lubricant and substratum), are especially phenols or naphthols having a sterically hindered hydroxyl group as well as the derivatives of dihydroxyaryl compound the hydroxyl groups of which are in 0- or p-position to each other. Examples of particularly valuable compounds which can be used are the monophenol derivatives such as 2,4-dirnethyl-6-tert.butylphenol, 2,6-di-tert.butyl-4-ethylphenol, 2,6-bis-(1-methylcyclohexyl)-4methylphenol, 2,6-di-tert.butyl-4-dimethyl-aminomethyl phenol, 2,2-methylene-bis-(4-methyl-6-tert.butyl phenol), 2,2'-thi0-bis- (4-methyl-6-tert.butylphenol) 4,4'-dihydroxy-2,2-dimethyl-5,5-di-tert.butyldiphenyl sulphide and diphenyl disulphide, 2,6-bis- 2'-hydroxy-3 -tert.butyl-5 -methylbenzyl 4-methylphenol,

derivatives of polynuclear phenols such as 2-tert.butyl-lhydroxynaphthalene, 4,6-di-tert.butyl-5-hydroxyindane, 5- hydroxyacenaphthene, polyvalent phenols and derivatives thereof: butyl pyrocatechin, octyl gallate, hydroquinone, butylhydroxy anisole, hydroquinone monobenzyl ether.

Of aminohydroxyaryl compounds, useful as antioxidant functional fluids according to the invention, those derivatives in which the amino and hydroxyl groups are in pposition to each other are particularly suitable. Examples are: p-hydroxy-diphenylamine, p-hydroxyoctyl aniline, phydroxy-N-y-aminopropyl aniline.

Heterocyclic compounds which can be used as antioxidants are exemplified by the following: phenothiazines or iminodibenzyls, e.g. those substituted by higher alkyl; phenosilazines, e.g. 5-ethyll0*,lO-diphenyl-phenosilazine; dihydroquinolines, e.g. 6-methoxyor 6-ethoxyor 6-ethylamino-2,2,4-trimethyl-1,Z-dihydroquinoline, or telomers thereof; or tetrahydroquinolines, e.g. 3-hydroxy-7,8-benzo- 1,2,3,4-tetrahydroquinoline.

Didodecyl selenide or Topanol CA sold by Imperial Chemical Company, a compound of the sterically hindered phenol type, may also be used as antioxidant.

Moreover, additives which improve or modify the properties of lubricant and other functional fluids containing as the essential functional component imides according to the invention can be mixed with the latter. Such additives are, for instance, antioxidants, high pressure additives, anticorrosives, agents to lower the solidification point and viscosity index improvers and/or thickeners.

Suitable high pressure additives in the functional fluids according to the invention are barium or calcium mahogany sulfonates, lower alkyl phosphites, phosphates, sulfurized sperm oil or the like; suitable viscosity index improvers are the polymethacrylate alkyl esters; suitable defoaming agents are, e.g. those based on silicone oil, and suitable anti-corrosives are, e.g. sarcosines and benzotriazoles.

Compositions of matter which are fluid at room temperature which can be used as functional fluids according to the invention having a thermal stability of at least 360 C. contain at least 25% by weight (calculated on the total weight of the composition) of imides of Formula I and up to 75% by weight of at least one functional fluid based on esters, aromatic ether, silicium compounds, melamines and high boiling mineral oil fractions. The proportions of the mixture in each case depend on the intended purpose. The invention also includes greases consisting of imides as defined and thickeners. Examples of suitable thickeners are metal soaps, montmorillonites, e.g. bentonite, phthalocyanines, violanthrones or graphite.

The following examples illustrate the particular suitability of the imides used according to the invention as synthetic lubricants and as hydraulic fluids. The units of measure of the metric system are used therein. Where not otherwise stated, the temperatures are given in degrees Centigrade.

PRODUCTION AND PROPERTIES OF N-ALKYL IMIDES OF FORMULA I USED ACCORDING TO THE INVENTION N0. ].-N n-dodecyl-cis-cyclohexane-],2-dicarbxylic acid imide: A mixture consisting of 308 g. (2 mol) of cis-cyclohexane-1,2-dicarboxylic acid anhydride, 390 g. (2.1 mol) of technical dodecylamine (Armour Co., Chicago, USA) and 200 g. of xylene is heated for 4 hours at 150. The reaction water formed is continuously removed from the reaction mixture as Water/xylene azeotrope by means of a water separator. By distillation under vacuum 699 g. of a product consisting mainly of N-ndodecyl-cis-cyclohexane-1,2-dicarboxylic acid imide are obtained. B.P. 161166 under 0.05 torr; n 20:1.4802, M.P. 3. The technical dodecylamine used contains 99.0% by weight of dodecylamine, 0.3% by weight of decylamine and 0.7% by weight of tetradecylamine. Pure N-n-dodecyl-cis-cyclohexane-1,2-dicarboxylic acid imide boils at 241-242.5/12 torr and the 11 20 is 1.4812.

In contrast, N-n-dodecyl succinimide, produced from succinic acid anhydride and technical dodecylamine, melts at 54-55 N0. 2.N-n-decyl-cis-cyclohexane 1,2 dicarboxylic acid imide: 1290 g. (8.4 mol) of cis-cyclohexane-1,2- dicarboxylic acid anhydride are heated at 120 in a 4.5 litre four-necked flask fitted with two inlet funnels, a

, thermometer and a combined water separator and reflux condenser. 1383 g. (8.8 mol) of technical decylamine (Fettamin 10 D of Farbwerke Hoechst A.G., Frankfurt am Main, Germany) are added dropwise to this mixture within 90 minutes, the temperature of the reaction mixture being kept between 120 and 150. Toluene is added dropwise simultaneously in order to remove the reaction water formed as toluene/water azeotrope from the reaction mixture. The imide formation is complete after 5 hours and the theoretical amount of 151 g. of water is removed. The reaction mixture isdistilled in vacuo. The first fractions, 66 parts, consists mainly of Fettamin D. The main fraction weighs 2460 g. and is a mix ture consisting mainly of N-n-decyl-cis-cyclohexane-1,2- dicarboxylic acid imide. B.P. 155158/0.01 to 0.02 torr; density at 20; 0.984; 11 20: 1.4823. Yield; 94.3%, calculated on the cis-cyclohexane-1,2-dicarboxylic acid anhydride. This product solidifies below 55. The Fettamin 10 D consists of 1.0% by weight of dodecylamine, 76.4% by weight of n-decylamine, 21.8% by weight of n-octylamine, 0.3% by weight of n-hexylamine and 0.5% by Weight of low boiling impurities.

Pure N-n-decyl-cis-cyclohexane-1,2 dicarboxylic acid imide boils at 228/ 12 torr; its 11 20 is 1.4826 and it solidifies under 30.

Pure N-n-decyl succinimide, on the other hand, melts at 4041".

N0. 3.N-n-0ctyl-cis-cyclohexane 1,2 dicarboxylic acid imide: 616 g. (4 mol) of cis-cyclohexane-1,2-dicarboxylic 'acid anhydride are heated to 120 as described in No. 2 and at this temperature 547 parts of technical octylamine (Armeen 8 D of Armour Co., Chicago, USA) are added dropwise to the mixture. The reaction water formed is continuously removed as toluene/water azeotrope. 1009 g. of a mixture consisting mainly of 6 N-n-octyl-cis-cyclohexane-1,2-dicarboxylic acid imide are then obtained by fractional distillation. B.P. 134-140/ 0.005 to 0.001 torr; n ZO; 1.4842; density at 20: 0.960. Calculated on the cis-cyclohexane-1,2-dicarboxylic acid anhydride, the yield is 95.0%. The technical octylamine used for this synthesis boils between 159-179 and consists of 4.5% by weight of n-hexylamine, traces of n-heptylamine, 95.5% by weight of n-octylamine and traces of decylamine.

Pure N-n-octyl-ciscyclohexane-1,2-dicarboxylic acid imide boils at 206207/ 11.5 torr; it solidifies below 55 and its refractive index n 20: is 1.4843. In contrast, pure N-n-octyl succinimide melts at 26.527.

N0. 4.N-n-hexadecyl-cis-I,2-cycl0hexane-1,2 dicarboxylic acid imide: A mixture consisting of g. (0.65 mol) of cis-cyclohexane-1,2-dicarboxylic acid anhydride and 168.5 g. (0.7 mol) of technical n-hexadecylamine, is heated for 3 hours at 165 while removing the reaction water and is then distilled. 238 parts of N-n-hexadexyl-cis-1,Z-cyclohexane-1,2-dicarboxylic acid imide are obtained. Yield: 97.8% calculated on the cis-cyclohexane-1,2-dicarboxylic acid anhydride; B.P. 192-202/ 0.1 torr; n 30: 1.4794. The melting point of this product is between 20-30", so that it is less suitable as a lubricant than substances No. 1 to No. 3. The technical hexadecylamine used consists of 84.1% by weight of n-hexadecylamine, traces of n-decylamine, 1.8% by weight of n-dodecylamine, 7.0% by weight of tetradecylamine, 1.1% by weight of pentadecylamine and 6.0% by weight of octadecylamine.

N0. 5.N-n--decyl-cis-3,6-end0methylene-cyclohexane- 1,2-dicarb0xylic acid imide: A mixture consisting of 328 g. (2 mol) of anhydride of cis-bicyclo[2,2,1]heptene- (2)-5,6-dicarboxylic acid and 333 g. (2.1 mol) of Fettamin 10 D (cf. No. 2) is heated to 150 and the reaction water is continuously removed as azeotrope. Distillation yields 571 g. of a mixture consisting mainly of N-n-decyl-cis-3,6-endornethy1ene-1,2,3,6 tetrahydrophthalic acid imide, which corresponds to 94.7% calculated on the above anhydride. B.P. 162-165 /0.5 torr; n ZO: 1.4912. This imide is catalytically hydrogenated with hydrogen by means of palladium charcoal at room temperature under 3 atmospheres excess pressure, whereupon a quantitative yield of 'a mixture consisting mainly of N-n-decyl-cis-3,6-endomethylene cyclohexane-1,2-dicarboxylic acid imide is obtained. B.P. 153/0.05 torr; 11 20: 1.4934; solidification point below 20.

N0. 6.-N-n-dodecyl-cis-3,6-end0melhylene cyclohexane-LZ-dicarbovcylic acid imide: 205.5 g. (1.25 mol) of cis-3,6-endomethylene-1,2,3,6-tetrahydrophthalic acid anhydride and 243 g. of technical n-dodecylamine (cf. No. 1) are heated to while removing the reaction water and then the mixture is fractionated.

93.0% by weight of N-n-dodecyl-cis-3,6-endomethylene-1,2,3,6-tetrahydrophthalic acid imide are obtained, corresponding to 93.0% by weight calculated on the above anhydride. B.P. 191194/0.01 torr; 11 20: 1.4913. This imide is catalyticaliy hydrogenated with hydrogen in the presence of palladium like No. 5 and then fractionated whereupon a mixture consisting mainly of N-n-dodecylcis-3,6-endomethylene cyclohexane-1,2-dicarboxylic acid imide is obtained. B.P. 172-176/0.005 torr; 22 20: 1.4897; yield 97.1% solidification point below 10.

The following examples illustrate the invention.

Example 1 Imide No. l is suitable for lubricating metal surfaces. To attain a quantitative comparison of its lubricant action with five usual commercial lubricants, the scar diameter was measured in a 4-ball wear machine. These measurements were obtained according to US. Federal Specifications Lubricants and related Products VV-L 791e. Method 6503: Load Carrying Capacity (means Hertz Load). This apparatus ran for 30 minutes at a speed of 1480 revs. per minute with a load of 40 kg.

using /z inch steel balls SKF A quality at a starting temperature of about 40. The results are summarised in the following Table 1.

cinimide can only be heated to at most 380. The useful liquid range of imide No. 1 is also extended by at least 60 compared with the corresponding succinimide.

TABLE 2 I II III IV V Change in viscosity after 6 hours treatment Viscosity in eentistokes Loss in weight 6 hours at temperatures given Substance at A.S.T.M. at in column IV, in perslope cent; final viscosity being measured at- 100 1*. 210 F. C. In percent 100 F. 210 F.

Irnide 1 39. 17 5. 50 0. 78 400 4. 54 9. 6 6. 4 N-n-dodecyl succinimide (from same amine as No. l) Solid 4. 38 380 3. 3 9

400 87. 8 Imide 2 32. 92 4. 77 0. 81 380 1. 9 3. 7 2. 0 400 2. 8 5. 9 2. 0 29. 21 4. 36 0. 82 380 2. 3.8 2. 1 56. 50 7. 14 0. 75 380 1. 6 -5. 2 1. 6 400 3. 6 2. 8 2. 6 Imide 5 66. 5 7.09 0. 80 380 4. 7 2. 8 1. 0 400 6. 3 5. 7 3. 2 Imide 6 71. 6 7. 83 0.77 400 7. 4 9.1 5. 6

1 Cannot be determined since substance is solid at 100 F. 2 Not measurable.

TABLE 1 Example 3 S diameter m To test the stability necessary for the lubricant powers substanfie used: (average of 3 measumments) of the imides according to the invention under oxidative n 1 0545 conditions, 25 ml. of the substance were exposed at a f' Sebacate 0-817 constant temperature to a stream of air of 2 litres per Dl'z'ethylhexyl SePacate 0-850 hour for 6 hours and the aldehydes formed by reaction Y Y adlpate 0-915 with hydroxylamine hydrochloride were acidimetrically Mineral oil (viscosity at 100 F.: 65.7 cst.) 0.898 Pentaphenyl ether (voscosity at 100 F.: 369

cst.) 1.154 Methylphenyl silicone (viscosity at 100 F.:

78.3 cst.) 1.953

(lubrication ceased even after 2 /2 mins.)

The imides Nos. 2-6 gave similar results in this lubricant test as imide No. 1. Because of its M.P. 5455, N-n-dodecyl succinimide could not be compared in this test.

Example 2 The imides Nos. 1-6 are also suitable at very high temperatures as lubricants and heat-transferring agents. The imides were tested as follows as to the thermal stability necessary for such uses:

A sample of 25 ml. of one of the imides given in column I of the following Table 2 was heated for 6 hours at 380 or 400 in a glass reaction tube of about 25 mm. diameter while simultaneously introducing nitrogen (2 liter per hour). The loss in weight at the end of this time is given in column IV, the alteration in viscosity in percent of centistokes, measured at 100 F. (37.8 C.) and at 210 F. (98.8C.) caused by this heat-ageing is given in column V of this table.

This table also shows other physical data of the compounds from which the suitablility of these stable, difficultly volatile imides as functional fluids and/or lubricants can be seen. Column II shows the viscosity measured at 100 F. (37.8 C.) and at 210 F. (98.8 C.) in centistokes, column III gives the so-called A.S.T.M. slope determined with the aid of the A.S.T.M. Standard Viscosity-Temperature Chart for Liquid Petroleum Products (Method D 341) at 100 F. and 210 F. The lower the A.S.T.M. slope figures of a fluid, the more suitable it is as lubricant. A value of over 1.0 means that the fluid is only very slightly suitable. A.S.T.M. is an abbreviation for American Society for Testing Materials, 1961 Race St., Philadelphia, Pa., U.S.A.

As can be seen from Table 2, imide No. 1 can stand heating up to 400 whereas the analogous dodecyl sucdetermined. This showed that imide No. 3 at a test temperature of 260 was more slowly oxidised than the corresponding succinimide at a test temperature of 226. This means that imides according to the invention can be used under oxidative conditions at at least 34 higher temperatures than the corresponding succinimide.

Example 4 A decisive property of a lubricant is that the system operated therewith can be advantageously sealed. To prove this in the case of the imides according to the invention, a strip of Viton A rubber which is suitable as gasket material (Viton A is a synthetic special rubber consisting of vinylidene fluoride-hexafiuoropropene mixed polymer made by Du Pont Co., Wilmington, Del, U.S.A.), the dimensions of which strip were 25.4 x 25.4 x 1.6 mm., was heated for 150 hours at 110 in imide No. 1. The increase in volume of the strip was +10.83%. The hardness was changed by 7.6 degrees. A similar Viton A rubber strip was tested analogously in imide No. 2. In this case the increase in volume was +285 6% and hardness was altered by 13.8 degrees.

The imides Nos. 3-6 had a similar effect on Viton A rubber. The imides Nos. 1-6 produced swell values with commercial silicon rubber similar to those produced with Viton A rubber. This also shows that the above imides do not unduly alter the nature of the tested sealing materials.

Example 5 In order to adapt the properties of lubricants and heat-transferring fluids to the desired use, it is important that they can be mixed with other base stocks. To test the behaviour of the imides according to the invention in this respect, tests were made as to their miscibility at 25 With various usual commercial lubricants and heattransferring agents. The mixtures produced were observed for 20 consecutive days at 0 and their viscosity was measured at the beginning and the end of this observation time. The viscosity in centistokes of the pure lubricant-s as well as of mixtures thereof was determined at F. (37.8 C.) and 210 F. (98.8 C.) and is given in column V of Table 3. Column VI shows the A.S.T.M. slope. Column I gives the second component of the mixture and column II shows the proportion thereof to imide No. 2. The immediate miscibility at 25 is given in column III, that after storing for 20 days at is given in Similar functional greases according to the invention are obtained by replacing the copper phthalocyanine thickener in the above example by one of the other thickeners mentioned hereinafter, namely bentonite, Violanthrone, graphite, or metal soap, e.g. lithium palmitate,

column IV, in both of Which cases, a means complete or lithium stearate, 1n amounts ranglng from to 35 homogeneity of the mixture. g. er 100 g. of the resulting mixtures.

TABLE 3 I II III IV V VI Proportions of mixture, parts Mixture Viscosity in centistokes Miseibility after at A.S.T.M. Substance X at d612 at slope Imide N0. 2 Substance X 100 F. 210 F.

Trimethylol propane tripelargonate tech 0 100 23. 7 4.8 0. 70 33 66. 6 25. 8 4. 8 0. 72 50 50 27.1 4.3 0.74 66.6 33.3 28.9 4.8 0. 76 2-diethylhexyl scbacate tech 0 100 12. 7 3. 3 0. 70 33.3 66.6 16.3 3.0 0.75 50 50 18.8 3.9 0.74 66.6 33.8 22.0 4.1 0. 77 Dioetylphthalate tech 0 100 29. 9 4. 3 0.84 33.3 66.6 31.0 4.4 0.34 50 50 31.3 4.6 0. s1 66. 6 33. 3 31. 7 4. 6 0.81 Tricresyl phosphate tech 0 100 29. 8 4. 1 0.87 33.3 66.6 30.4 4.2 0. 86 50 30.6 4.2 0.86 66.6 33.3 31.7 4.4 0. s4 Polyran M 25 (Bayer) a mixed polymer of cyclic 0 100 80.1 14.4 0.54 ethers. 33. 3 66. 6 60. 5 10. 0 0. 61 50 50 52.5 8.5 0.65 66.6 33.3 45.0 7.0 0.70 Peutaphenyl ether (Monsanto 08-124) 0 100 309. 5 13. 5 0. 89 33. 3 66. 6 124. 4 9. o 0.83 50 50 83.5 7.5 0.82 66.6 33.3 57.2 6.3 0.81 Motor Oil SAE 20 (usual commercial mineral oil) 0 100 65. 7 8. 4 0.71 33.3 66.6 47.0 6.5 0.75 50 50 41.5 6.0 0.75 66.6 33.3 37.5 5.5 0.76 Silicon Fluid DO 200 (Dow Corning), a methyl- 0 100 4.2 1.9 0.59 phenyl silicone. 33. 3 60. 6 7. 7 2. 6 0. 66 50 50 10.3 2. 72 0. 71 66.6 33.3 14.6 3.6 0. 70 2,4-bis-(dibutylamino)-6-(didodecylamino)-s-triaziud 0 100 134. 0 15. 0 0.62 50 50 51.4 7.1 0.72 00 49.0 6.9 0.73 70 30 43.4 6.3 0.74 Imide N o. 2 alone 100 0 32.9 4. 8 0.81

Both at 0 and at 25 imide No. 2 can also be mixed Example 7 in any proportion with a bis-(phenoxyphenyl)-ether, (e.g. 99 of imide Na 2 and 1 of iminodibenzyl are DOW ET'378 3 Dow chemllgal 11, g g stirred together until the latter has completely dissolved. i i exyl S1 mate me y Compared with the pure imide, the mixture obtained has phenyl s1l1con 011 (cg. s1l1con DC 550 Fluid of Dow S O f Mu improved stability to oxidatlon. Corn1ng Co., Midland, Mich. U.S.A. or 55 Similar results are obtained if the usual antioxidants lalid SIIICOPS "3 wlth uty ammo) used for the purpose in industry are added to the imides b H h No. 1 and Nos. 3-6 in amounts of 0.01 to 5%, calculated The i mides Nos. 1 and 3- 6 have su stant1a yt 6 same on the imide to be stabilised to oxidation. miscibility with the synthetic lubricants shown in Table III as imide No. 2. Example 8 Example 6 97.5 g. .01 imide No. 1, 1.5 g. of dibutyl phosphite as The use of the imides according to the invention or h P afldltl've and-1 of P f Y P S the production of greases is shown in the following exarfllne 3 antlqXlfiallt are lulX d by st rrlng. Compared ample. With the pure 1m1de, the mixture obtained has lmproved 3 of copper phthalocyanine, 4 f imide 1 and stability to oxidation and the lubricant film has better 40 ml. of benzene are stirred very quickly in an Ultral a carrylng P p y slmilar TeSPItS Obtained if the turax mixer for 15 minutes. Another 20 g. of this 1, 3 to 6 are mlxed Wlth hlgh Pressure imide are then added and the mixture is Stirred very additives and antloxidants mentioned hereinbefore, in quickly for another 45 minutes amounts of about 0.2 to 5 calculated on the weight of The homogeneous mass so obtained is worked on a the lmlde to be stablhzed to oxldatlonglass surface with a spatula until the benzene has evapo Example 9 rated. The mass obtained is heated for 2 hours at 150 99 8 f N 2 d 0 2 f b I and after cooling is again Worked with a spatula. The 2 1 9 g fi are product so formed is a soft grease which can be Well i h ollnpar 2 pure P e mlxmre Worked up. It was found to have the following greasing i as 658 corroslve ac Damon M y on Copper properties and its alloys.

Penetrati0n.-A.S.T.M. D 140356T, 1958 edition), Example 10 unworked up: 305, Worked up: 328. 97 g. of imide No. 1 and 3 g. poly-2-ethylhexylmeth- Dropping p0int.-A.S.T.M. D 566-42 (1957 edition), 7 acrylate (HF 825 produced by Rohm & Haas Co., Philworked up: over 238 (IP. 132/57).

adel-phia, Pa., U.S.A.), as visocsity improver, are homo- 1 l geneously mixed by stirring. This mixture has :a lower solidification point than the pure imide No. 1.

I claim:

1. A method of lubricating hydraulically operating parts of a mechanical system in frictional engagement with each other, comprising inserting between said parts so engaged a film of an imide of the formula CH CO Carma I N-R OH wherein R and R" each represent hydrogen and taken together, they represent a lower alkylene group of from 1 to 2 carbon atoms, and

R represents an alkyl group of from 6 to 18 carbon atoms in a straight chain,

thereby lubricating said engaged parts.

2. A functional fluid, consisting essentially of a major amount of an imide of the formula CH C O wherein R' and R" each represent hydrogen and taken together, they represent a lower alkylene group of from 1 to 2 carbon atoms, and

R represents an alkyl group of from 6 to 18 carbon atoms in a straight chain,

the balance consisting of a minor amount of at least one adjuvant selected from the group consisting of an antioxidant compatible with and stabilizing said imide, an anticorrosive agent capable of protecting metal surface in contact with said imide against corrosion by the latter, an anti-foaming agent compatible with said imide, and a polymethacrylate viscosity index improver.

3. A grease, consisting essentially of a major amount of an imide of the formula wherein R and R" each represent hydrogen and taken together, they represent a lower alkylene group of from 1 to 2 carbon atoms, and

R represents an alkyl group of from 6 to 18 carbon atoms in a straight chain,

the balance consisting of a minor amount of at least one adjuvant selected from the group consisting of an antioxidant compatible with and stabilizing said imide, an anticorrosive agent capable of protecting metal surface in contrast with said imide against corrosion by the latter, an anti-foaming agent compatible with said imide,

and a polymethacrylate viscosity index improver, and a thickener in sufficient amount to impart to the entire mixture the consistency of a grease.

4. A composition consisting of at least 25% and up to by weight of a lubricant imide of the formula orn R o I om n" wherein R and R" each represent hydrogen and taken together, they represent a lower alkylene group of from 1 to 2 carbon atoms, and

R represents an alkyl group of from 6 to 18 carbon atoms in a straight chain,

a minor amount of at least one adjuvant selected from the group consisting of an antioxidant compatible with and stabilizing said imide, an anticorrosive agent capable of protecting metal surface in contrast with said imide against corrosion by the latter, an anti-foaming agent compatible with said imide, and a polymethacrylate viscosity index improver; the balance consisting of a functional fluid selected from the group consisting of organic ester lubricant, polyaryl ethers, polyalkyl melamines, high boiling phosphoric acid esters, high boiling mineral oils, silicone oils and esters of ortho-silicic acid.

6. A functional fluid as defined in claim 2 wherein the imide in N-n-decyl-cyclohexane 1,2 dicarboxylic acid imide.

7. A functional fluid as defined in claim 2 wherein the imide is N-n-dodecyl-cyclohexane-1,2-dicarboxylic acid imide.

8. A functional fluid as defined in claim 2 wherein the imide is N-n-octyl cyclohexane 1,2 dicarboxylic acid imide.

References Cited by the Examiner UNITED STATES PATENTS 3,078,228 2/1963 Smith et al. 252-51.S X 3,151,079 9/1964 Archer 25251.5 3,208,939 9/1965 Latos et al. 252--51.5 X

DANIEL E. WYMAN, Primary Examiner.

P. P. GARVIN, Assistant Examiner. 

4. A COMPOSITION CONSISTING OF AT LEAST 25% AND UP TO 75% BY WEIGHT OF A LUBRICANT IMIDE OF THE FORMULA 